Fudoh's ode to old display technology

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Tempest_2084
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Re: Fudoh's ode to old display technology

Post by Tempest_2084 »

Josh128 wrote:Increases or decreases screen voltage. ie it will brighten or darken the screen.
Ah ok. I don't need to mess with that then.

Ok I opened my set up today and attempted to adjust the yoke. I only loosened the screw a little (about a turn and a half) so the yoke doesn't move on its own. However all I can really do is rotate the screen, I'm not having much if any affect on the convergence other than making it slightly worse in the lower right corner. Do I need to loosen the screw more to actually move the yoke rather than simply rotating it or do I need to just be a bit more forceful? Part of my problem is I'm not 100% sure where to grab the yoke when I'm adjusting. The plastic ring has a wire around it for the built-in screen rotation adjustment so I'm afraid to grab that for fear of damaging it (although it looks pretty sturdy). I took two pictures of my yoke (see below), where should I grab it to do some serious adjustments?

I think I mentioned it before, but there's a second screw further back behind the convergence rings (you can see it in the second picture), do you think I need to loosen that to move the yoke around?
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Josh128
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Re: Fudoh's ode to old display technology

Post by Josh128 »

It looks like just the screw closest to the yoke, the second looks like its for that coil assembly on the neck. What kind of set is that? Also, I didnt see pictures of your problem, did you post a pic of a crosshatch?

Adjusting yoke tilt is for dynamic (non center) convergence after you have already gotten good static (center) convergence from adjusting the rings. The DY is probably "stuck" to the rubber wedges between it and the tube. You need to fully loosen that closest screw and back the yoke off of the wedges. You will then need to remove the wedge that is holding the yoke from tilting in the direction you want to adjust. You will then need to re-insert the wedge, tape it, and tighten the yoke.
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Tempest_2084
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Re: Fudoh's ode to old display technology

Post by Tempest_2084 »

Josh128 wrote:It looks like just the screw closest to the yoke, the second looks like its for that coil assembly on the neck. What kind of set is that? Also, I didnt see pictures of your problem, did you post a pic of a crosshatch?

Adjusting yoke tilt is for dynamic (non center) convergence after you have already gotten good static (center) convergence from adjusting the rings. The DY is probably "stuck" to the rubber wedges between it and the tube. You need to fully loosen that closest screw and back the yoke off of the wedges. You will then need to remove the wedge that is holding the yoke from tilting in the direction you want to adjust. You will then need to re-insert the wedge, tape it, and tighten the yoke.
It's a KV27-FS100

I posted pictures a few posts back (previous page about a quarter of the way down), here they are again. It's the dynamic convergence that I need to fix. You're probably right in that I need to unstick it from the wedges. Hopefully I don't actually have to remove the wedges though.
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Tempest_2084
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Re: Fudoh's ode to old display technology

Post by Tempest_2084 »

Josh128 wrote:It looks like just the screw closest to the yoke, the second looks like its for that coil assembly on the neck. What kind of set is that? Also, I didnt see pictures of your problem, did you post a pic of a crosshatch?

Adjusting yoke tilt is for dynamic (non center) convergence after you have already gotten good static (center) convergence from adjusting the rings. The DY is probably "stuck" to the rubber wedges between it and the tube. You need to fully loosen that closest screw and back the yoke off of the wedges. You will then need to remove the wedge that is holding the yoke from tilting in the direction you want to adjust. You will then need to re-insert the wedge, tape it, and tighten the yoke.
If I want to fix horizontal sagging on the bottom would I move the yoke left or right?
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Josh128
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Re: Fudoh's ode to old display technology

Post by Josh128 »

Yes. Thats how its supposed to work.
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Re: Fudoh's ode to old display technology

Post by Tempest_2084 »

So I was moving the yoke around to fix the geometry and the two wedges holding it in place fell out. Now I have this issue:
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I know where the one goes, it was right in the center on the top of the yoke and I have a picture of where it was. The second one however was on the upper right of the yoke (from the back about 2 o' clock) but that's all I really know. It doesn't seem to want to stay in anywhere now. Is my CRT screwed now or can this color distortion be fixed. I imagine this has something to do with the yoke being too far forward or backwards but I can't seem to figure it out. I just knew I was going to screw something up...

Help!

I also saw that there was a plug that wasn't plugged in. No idea if it was ever plugged in or not, I can't see anything obvious that it would go to. It's the one with the gray wires and one yellow wire on the left side of the first picture. The closest marking on the board says To V Board.
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Tempest_2084
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Re: Fudoh's ode to old display technology

Post by Tempest_2084 »

AH HA! I see it! It's on the neckboard! Maybe this is what's causing my problems? Which way does it go in? Yellow wire on top or bottom?
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tongshadow
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Re: Fudoh's ode to old display technology

Post by tongshadow »

Tempest_2084 wrote:I imagine this has something to do with the yoke being too far forward or backwards but I can't seem to figure it out.
Yea thats it, just a standard purity issue.
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Re: Fudoh's ode to old display technology

Post by Tempest_2084 »

tongshadow wrote:
Tempest_2084 wrote:I imagine this has something to do with the yoke being too far forward or backwards but I can't seem to figure it out.
Yea thats it, just a standard purity issue.
I think it's more than a standard purity issue, but like I said there's a cable that popped out the neck board that I'm trying to figure out how it goes in. Maybe that's causing some of the problems?
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Re: Fudoh's ode to old display technology

Post by tongshadow »

I have never worked on Sony TVs before but theres generally only 1 cable that goes to the neck of a CRT: the RGB output connection cable, which also can have pins for the heater voltage and 200V or so to drive the cathodes. On fancier sets there's also a cable for the velocity modulation circuit and another separate 3/4 pin cable for the VM coil itself (attached to the necktube itself). Disconnecting the latter shouldnt result in purity issues, and some even say it improves the picture, but it's a Sony and they use unique designs not seen anywhere else, like 2 separate boards on the tube's neck.
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Re: Fudoh's ode to old display technology

Post by Tempest_2084 »

Got the cable back in (yellow on the bottom), but I think the set is hosed. No amount of adjusting the yoke is fixing the colors on the edges of the screen (or having any effect actually). I'm not sure what I'm doing wrong!
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Tempest_2084
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Re: Fudoh's ode to old display technology

Post by Tempest_2084 »

So this is where I'm at right now. I fixed the major color issue I was having (I just had to push the yoke forward until it popped into a groove or something), but as you can see I need to tweak the geometry and there's still some color purity issues on the left side. Which way do I move the yoke to fix that?
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Josh128
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Re: Fudoh's ode to old display technology

Post by Josh128 »

Its hard to say which way you need to move it. But it looks like you've definitely improved the lower dynamic convergence quite a bit over your original pictures here.

You likely are very close and just need to adjust the tilt by a single degree or fractions of a degree. Sometimes you can accomplish this type of fine adjustment by slowly sliding a wedge in, the thickness changes on the wedge will do the tilting for you. But it looks like you are definitely on the right track.
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Re: Fudoh's ode to old display technology

Post by Tempest_2084 »

Josh128 wrote:Its hard to say which way you need to move it. But it looks like you've definitely improved the lower dynamic convergence quite a bit over your original pictures here.

You likely are very close and just need to adjust the tilt by a single degree or fractions of a degree. Sometimes you can accomplish this type of fine adjustment by slowly sliding a wedge in, the thickness changes on the wedge will do the tilting for you. But it looks like you are definitely on the right track.
That's a good idea. Right now I have no wedges in there at all. Currently I have the color on the left side of the screen fixed but when I move the yoke it tends to go back to being yellow. I have fixed the lower right corner but there's still done convergence issues on the bottom horizontal line.

Since I have it mostly there I'll tighten down the screw more and the move it very slightly until I dial it in.

It doesn't show in this picture but I'm having some linearity issues with the left side of the screen. The squares on the left are smaller (thinner) than the other squares. How do I fix that?
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ASDR
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Re: Fudoh's ode to old display technology

Post by ASDR »

Josh128 wrote: Magnetic permeability of a material near a coil changes (increases) the coils inductance. This is the same principle all high efficiency transformers utilize and why they have an iron or ferrous core. These strips affect the magnetic field produced by the DY in the area under the coil in which they are placed. This affects how each cathode ray is deflected in that region of the tube. Permalloys super high permeability makes it effective even in thin strips required to slide under the yoke. That said, expect to be frustrated when using strips-- most of the time, you can only get limited benefits as a strip affects all the cathode rays, not just one. If your red is separated in the top right corner from your blue and green, they will all move when you play with a strip underneath them, which also affects geometry in that corner. By using different depths and angles of the strip, sometimes you CAN get corner convergence a bit better, but its often difficult, frustrating, limited, and not the magic bullet you might be hoping it is.
That's a great explanation, thanks!

I agree that it's a total PITA. This weekend I was trying to fix a corner that has red separated vertically and I just couldn't get it any better. Either I fix red and have blue bulging out or I have everything in alignment but now the entire corner is dragged upwards :/

I've made some more strips:

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both the permanent magnets and the permalloy ones from box cutter blades work fine and have useful effects.
Josh128 wrote: Also, despite what others have said, tilting the yoke does work for adjusting dynamic convergence, its actually the most effective way to do it when you dont have PVM-like adjustment coils and controls. Thing is, its like an art. Its ULTRA sensitive. You may need to tilt the yoke 1mm up, down, or diagonally to pull a red or blue extruding beam back into the white line where its supposed to be. THEN you have to place the wedge under it then tighten the clamp to hold the yoke there all without anything moving. THEN you have to re-examine other areas of the screen that you werent having a problem with to see if youve introduced a problem. In other words, its not easy. :mrgreen:
My experience as well, it's very finicky. On newer Sony TVs there are dynamic convergence controls & coils on the top of the yoke and then there's also these magnet pieces that slide into the side. Even very old PVMs have these.

Touching the yoke is a PITA...
H6rdc0re wrote:On my Sony PVM I had to remove the anti glare filter because it was damaged. Now I find the brightness to be much higher and the black levels are much worse. Does anyone know if it's possible to use a different anti glare filter from for example a car window?
Hm, can't get things looking proper with just the usual contrast/brightness controls? Might have to exercise some more light control in the room, but I haven't noticed any other adverse effects :/
Tempest_2084 wrote:...
Those color issues were the purity issues I told you about, happens when you move the yoke too much forwards/backwards. You should really take pictures BEFORE you do stuff to your TV so you know where cables etc. were. Also did you read the service manual like I suggested? You have plenty of controls on your yoke and I think you got Y splitter magnet or whatever it was called, there's lot of useful things to be tweaked there!
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Re: Fudoh's ode to old display technology

Post by ASDR »

Advice needed - Can a TV degauss my magnet? :shock:

I had this Sony for a while, great condition, never really put it into rotation because of the very common corner of total fuckedness:

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It's actual worse than it looks. It's not just the corner, the entire upper-right part of the screen sags down and it's super noticeable when scrolling or when a straight line/box etc. is on the screen.

I originally tried to fix it by placing a small ferrite bar magnet close to the yoke. I was able to fix the sag of the horizontal lines but introduced all kinds of other issues like a curl of vertical lines near the top and a bow on the right screen edge.

This weekend I thought I give it another shot and removed all magnets, yoke strips etc. and see if I can fix it for good. After some hours of messing around and experimenting I figured out placing a stronger magnet further away from the yoke did a better job. It gently moved everything up a little without introducing too many other issues. Stuff close to the yoke is good for affecting a single small spot like a bit of a corner, further seems to be better for my issue. Here:

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(ignore some of the white tape, just added temporarily to mark location etc.)

After all that work geometry and convergence were looking decent:

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Massive improvement and good enough for an FD Trinitron.

I then closed up the TV and gave it another go. To my great surprise, things were looking bad again. I opened up the TV, thinking I had accidentally dislodged something or the speakers in the back housing were causing issues etc. No luck, nothing had moved a millimeter and things still looked broken :/

Then it dawned on me that while adjusting the set I turned it on and off a couple of times to enter or leave the service menu, but if you do that quickly the degausser never fires. But it definitively had after turning it off for a while when reassembling it. If you look at the placement of my magnet, it's quite high and inside one of the two loops of the degaussing coil. I also noticed that when placing another new magnet directly where the installed one is my geometry mostly moves back to where it's supposed to be. Hm.

Do you think my theory of the TV degaussing my correction magnet is plausible? Can I just not place magnets that far away from the yoke, in the upper/lower area where the two coils on this set are placed?
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Re: Fudoh's ode to old display technology

Post by Josh128 »

Depending on the makeup of the magnet its possible, but more likely is the scenario that you moved/rotated the TV after closing it up, causing a purity issue from the earths magnetic field.
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Re: Fudoh's ode to old display technology

Post by ASDR »

Josh128 wrote:Depending on the makeup of the magnet its possible
Ferrite bar magnets?

If I add another magnet or two I can get things back to how they looked like before the degaussing happened, but then I guess those would just be degaussed as well.

I also quickly tried to just take the magnets off, now I have another issue. Seems like overnight the tube has taken magnetism from the correction magnets and I now have a big dent and some severe purity issues in that spot. If the sets build in degausser can't take care of this I think I need to buy an external degaussing coil. Oh boy.
Josh128 wrote: , but more likely is the scenario that you moved/rotated the TV after closing it up, causing a purity issue from the earths magnetic field.
I think we can safely exclude that as the issue. I didn't move/rotate it any significant way during testing and reassembling and moving / rotating it a bit on the work table doesn't change anything, certainly nothing quite so big and confined to a single corner. The earth's magnet field might rotate the picture or maybe cause purity issues, but it does not cause anything like that.
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Tempest_2084
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Re: Fudoh's ode to old display technology

Post by Tempest_2084 »

ASDR wrote: I also quickly tried to just take the magnets off, now I have another issue. Seems like overnight the tube has taken magnetism from the correction magnets and I now have a big dent and some severe purity issues in that spot. If the sets build in degausser can't take care of this I think I need to buy an external degaussing coil. Oh boy.
Ouch. This is why I'm afraid to play with any magnets on my set other than those weak convergence strips. I hope there's no permanent damage because your geometry looks great. What pattern did you use to adjust it? I'm currently using the red/white grid, but people are telling me that I need an all white grid because the red hides convergence issues (and given my past convergence issues I agree).
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Re: Fudoh's ode to old display technology

Post by MKL »

Yes, purity magnets should be placed in the area where the internal magnetic shield (that gets degaussed like the mask) is not present (i.e. not too far away from the yoke) or their effect will vanish after degaussing.

https://i.imgur.com/TEbP6ba.jpg

Here's a view of a CRT innards showing the shield and its square cutout:

https://i.imgur.com/VedNx7k.jpg
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Re: Fudoh's ode to old display technology

Post by H6rdc0re »

ASDR wrote:Hm, can't get things looking proper with just the usual contrast/brightness controls? Might have to exercise some more light control in the room, but I haven't noticed any other adverse effects :/
In a fully dark room I'm finding the black levels disappointing to be honest. In a room with the lights on it's even worse. On some of my CRT PC monitors the black levels are great. Could it be the SMTPE phosphors having worse black levels than P22 phosphors? Or could it be a wrong G2 voltage? Please note I have two PVM-20L4s both having the same disappointing black levels. I highly doubt G2 voltage is set wrong on both. Also both PVMs have low hours (less than 5.000).

I really hope an alternative anti glare filter could improve black levels but nobody seems to know what anti glare filter would be the best choice if any.
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Re: Fudoh's ode to old display technology

Post by fernan1234 »

H6rdc0re wrote: In a fully dark room I'm finding the black levels disappointing to be honest. In a room with the lights on it's even worse. On some of my CRT PC monitors the black levels are great.
That's almost certainly because any PC CRT you've used has dark anti-glare coating or film, since they were made for typical use in bright-lit work spaces. PVMs and such in turn were for light-controlled if not blacked-out rooms in mind, but it is true that even in those conditions the non-tinted tubes don't do great when it comes to contrast.

I don't know of any anti-glare filter you can buy that would be satisfactory. Everything I found when I looked into it had a shiny finish and added even more reflection, and although it did bring black levels down it did so at the cost of brightness loss that is difficult to compensate.
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Re: Fudoh's ode to old display technology

Post by Tempest_2084 »

Someone in another forum suggested that I could adjust the three dials on the yoke to adjust the convergence. Does anyone know what these dials do exactly? They're marked VR1, VR2, and VR3.
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Re: Fudoh's ode to old display technology

Post by maxtherabbit »

H6rdc0re wrote:
ASDR wrote:Hm, can't get things looking proper with just the usual contrast/brightness controls? Might have to exercise some more light control in the room, but I haven't noticed any other adverse effects :/
In a fully dark room I'm finding the black levels disappointing to be honest. In a room with the lights on it's even worse. On some of my CRT PC monitors the black levels are great. Could it be the SMTPE phosphors having worse black levels than P22 phosphors? Or could it be a wrong G2 voltage? Please note I have two PVM-20L4s both having the same disappointing black levels. I highly doubt G2 voltage is set wrong on both. Also both PVMs have low hours (less than 5.000).

I really hope an alternative anti glare filter could improve black levels but nobody seems to know what anti glare filter would be the best choice if any.
just turn down the screen voltage, ez pz
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Re: Fudoh's ode to old display technology

Post by ASDR »

Tempest_2084 wrote: Ouch. This is why I'm afraid to play with any magnets on my set other than those weak convergence strips. I hope there's no permanent damage because your geometry looks great. What pattern did you use to adjust it? I'm currently using the red/white grid, but people are telling me that I need an all white grid because the red hides convergence issues (and given my past convergence issues I agree).
It all worked out, don't be discouraged :-)

You need like all the patterns. The red grid of course has the issue that it hides red convergence issues. I find the fine grid is really good to adjust convergence and fine corner geometry and make sure the edges line up, but I also can't see 'larger scale' distortion on it. Basically, on the usual red grid you can make sure linearity is great and that overall there's no wobblyness, but it's very course so you can't see minor errors close to the edge or whatever falls between the grid lines. The linearity screen where you can add a grid and dots is also another great one. Basically, adjust stuff and look at 3-5 different screens. I have it all the time that I think I got a setting or magnet just right and then it looks like total crap on another pattern.
MKL wrote:Yes, purity magnets should be placed in the area where the internal magnetic shield (that gets degaussed like the mask) is not present (i.e. not too far away from the yoke) or their effect will vanish after degaussing.

https://i.imgur.com/TEbP6ba.jpg

Here's a view of a CRT innards showing the shield and its square cutout:

https://i.imgur.com/VedNx7k.jpg
Perfect, just the info I needed.
H6rdc0re wrote: In a fully dark room I'm finding the black levels disappointing to be honest. In a room with the lights on it's even worse. On some of my CRT PC monitors the black levels are great.
Hm, I have to admit that I only ever had to remove the screen/foil from a PC CRT and my PVMs either never had them or had them already removed, so I'm not sure. On my PC CRT it was no big deal, quick readjust and light control. But like others have said, PVMs often have these very grey screens, they were clearly made for professional environments with ambient light control.
Tempest_2084 wrote:Someone in another forum suggested that I could adjust the three dials on the yoke to adjust the convergence. Does anyone know what these dials do exactly? They're marked VR1, VR2, and VR3.
I'm always yelling about them! :-) And the service manual! It should tell you what these do, probably TLV, YCH and HTRAP (there's a picture explaining what these are in basically every service manual). The service manual also has schematics that'll tell you where unplugged cables are supposed to go, it'll say something like 'To DY' or 'To D board'.
Tempest_2084 wrote:
Josh128 wrote:Increases or decreases screen voltage. ie it will brighten or darken the screen.
Ah ok. I don't need to mess with that then.
Maybe. If G2/Screen is set wrong this can also cause issues like visible retrace lines and just below that some kind of effect that looks like focus is wrong. I'd give it a quick adjust.
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Re: Fudoh's ode to old display technology

Post by ASDR »

Ok, quick update!

The internal Carl Friedrich coil (Gauss and I are on a first name basis now) was able to take care of the magnetization that I caused to the tube. Geometry and purity restored. Guess I can put off buying a degaussing coil a while longer.

I did some more experiments and it's pretty clear the Carl Friedrich thing is demagnetizing my magnet. So I went back and tried to get the geometry and convergence in shape with weaker magnets close to the yoke. Here:

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Convergence strip, round ferrite magent and bar ferrite magnet did the trick. Setup survived reasssembly and a few degaussing cycles. Results:

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I'm happy. Also, I swear this looks way better in person. There's this bowing out at the bottom that I just don't see in front of the screen (asked 2nd person to verify in case I've gone fully crazy). Maybe I'm sitting in front of the screen at a weird angle, in any case, worst case I have to adjust the lower corner pin or such.

What I've learned:

- Don't use strong magnets, even far away from the yoke. They'll eventually magnetize the tube/grill
- Don't place magnets inside the Carl Friedrich coil loop thing (MKL - Thanks for confirming and the linked pictures!!)
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Re: Fudoh's ode to old display technology

Post by SuperSpongo »

Very nice results!

When I took geometry shots with my Galaxy S7 I swear they also looked wonkier than the actual picture shown by the tube. I think that the camera added some distortion.
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Re: Fudoh's ode to old display technology

Post by Tempest_2084 »

ASDR wrote: I'm always yelling about them! :-) And the service manual! It should tell you what these do, probably TLV, YCH and HTRAP (there's a picture explaining what these are in basically every service manual)..
I think I did see references to that in the manual but the picture wasn't where they are on my set (it's the correct manual though) so I thought maybe that wasn't what they were. I can look again though.

So these ARE things I should mess with to fix my convergence issues? Still not 100% sure what they adjust, the manual is a bit confusing:

https://www.manualslib.com/manual/69674 ... =14#manual
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Re: Fudoh's ode to old display technology

Post by Tempest_2084 »

ASDR wrote:Ok, quick update!
Amazing results! I think you mentioned it before, but what was your process for doing this? I current have my grid in an 'okish' state (it needs some adjustments to the sides and the bow on the top and bottom) but I need to figure out how I want to proceed from here and not screw up what I've already done. I still have some minor horizontal convergence issues in the lower right area.
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Re: Fudoh's ode to old display technology

Post by Tempest_2084 »

What's causing the yellowish color distortion on the left side of the screen? I can't seem to get that fixed. Do I need to remove the wedge start over again? Also, as you can see I'm having some linearity problems on the sides, should I bother with that right now or try and get the color issue taken care of?

My gut says that I need to take the wedge out and pull the whole yoke closer to the front. I think that's generally what causes these kinds of issues. However it seems like no matter what I do it looks like it goes away but when I put a wedge in to keep the yoke in position the yellowish color is back by the time I go around front. It's not magnetization (at least I don't think) as I can move it around if I really play with the yoke, but oddly enough it is current right near where the speaker is. My only other idea is that it could have something to do with that coil that goes around the yoke for adjusting the tilt, but that thing is super heavy shielded and I think any changes I saw while wiggling it were because I was wiggling the yoke unintentionally.

What should my next steps be?
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